A body composition monitor calculating body composition of a subject using a bioelectric impedance method has conventionally been available. Such a body composition monitor is used for health care management of the subject. The methods of calculating (methods of estimating) the body composition are various, depending on devices.
For example, a method of calculating body composition based on impedance between both hands or both feet is available. Japanese Patent Laying-Open No. 62-169023 (hereinafter Patent Document 1) discloses measurement of weight of adipose tissues in body by measuring impedance between foot and foot or between hand and hand with electrodes brought in contact with the foot or the hand of a subject, for measuring impedance between end portions of the body. In addition, Japanese Patent Laying-Open No. 5-337096 (hereinafter Patent Document 2) discloses the feature that an electrode terminal plate for application and an electrode terminal plate for sensing are provided in two grip portions held by left and right hands, respectively and that a probe measuring body impedance between both hands is included.
In addition, a method of calculating body composition based on impedance of a whole body (between hand and foot) is available. Japanese Patent Laying-Open No. 2001-157672 (hereinafter Patent Document 3) discloses measurement of bio-impedance between an electrode for hand and an electrode for foot in such a manner that electrodes for left foot and right foot for application of a high-frequency signal are electrically connected and electrodes for left foot and right foot for measuring a resistance potential are electrically connected. Japanese National Patent Publication No. 10-510455 (hereinafter Patent Document 4) discloses operation of body composition by measuring impedance for each body part in such a manner that eight electrodes to be brought in contact with a right palm, a right thumb, a left palm, a left thumb, a right front sole, a right rear sole, a left front sole, and a left rear sole respectively are provided and two electrodes to which an alternating current is fed from these electrodes and other two electrodes for measuring a potential difference are selected.
Moreover, as shown in Japanese Patent Laying-Open No. 2005-230120 (hereinafter Patent Document 5), a body composition measurement device having means for switching between an 8-electrode mode (a mode in which eight electrodes brought in contact with both hands and both feet are used) and a 4-electrode mode (a mode in which four electrodes brought in contact with at least one measurement site are used) has also been proposed.    Patent Document 1: Japanese Patent Laying-Open No. 62-169023    Patent Document 2: Japanese Patent Laying-Open No. 5-337096    Patent Document 3: Japanese Patent Laying-Open No. 2001-157672    Patent Document 4: Japanese National Patent Publication No. 10-510455    Patent Document 5: Japanese Patent Laying-Open No. 2005-230120